1. Field of the Invention
The present invention relates to a spin-valve thin film element in which electric resistance changes depending upon the relation between the fixed magnetization direction of a pinned magnetic layer and the magnetization direction of a free magnetic layer affected by an external magnetic field, and a method of manufacturing the thin film element. Particularly, the present invention relates to a spin-valve thin film element with excellent stability in which the magnetic domain of a free magnetic layer can be sufficiently controlled, and a method of manufacturing the thin film element.
2. Description of the Related Art
FIG. 15 is a perspective view showing an example of thin film magnetic heads.
This thin film magnetic head is a floating type which is mounted on a magnetic recording medium such as a hard disk device or the like. In the slider 251 of the thin film magnetic head shown in FIG. 15, the side 235 which faces the upstream side in the moving direction of the disk surface is the leading side, and side 236 is the trailing side. In the surface of the slider 251 which faces the disk are formed rail-shaped ABS (air bearing surfaces: the floating surfaces of the rails) 251a and 251b, and air grooves 251c. 
Furthermore, a magnetic core 250 is provided on the end surface 251d on the trailing side of the slider 251.
The magnetic core 250 of the thin film magnetic head of this example is a combination type magnetic head having the structure shown in FIGS. 16 and 17, in which a MR head (reading head) h1 and an inductive head (writing head) h2 are laminated in turn on the trailing side-end surface 251d of the slider 251.
In this example, the MR head h1 comprises a lower shielding layer 253 made of a magnetic alloy and formed on the trailing side end of the slider 251 serving as a substrate, and a lower gap layer 254 provided on the lower shielding layer 253. A magnetoresistive element layer 245 is laminated on the lower gap layer 254, and an upper gap layer 256 is formed on the magnetoresistive element layer 245. An upper shielding layer 257 is formed on the upper gap layer 256 so that the upper shielding layer 257 also serves as a lower core layer of the inductive head h2 provided thereon.
The MR head h1 causes a change in resistance of the magnetoresistive element layer 145 according to the presence of a small leakage magnetic field from a magnetic recording medium such as a disk of a hard disk device or the like to read the recording content of the recording medium by reading the change in resistance.
The inductive had h2 comprises a gap layer 264 formed on the lower core layer 257, and a coil layer 266 having a spiral planar pattern. The coil layer 266 is surrounded by a first insulating material layer 267A and a second insulating material layer 267B. An upper core layer 268 is formed on the second insulating material layer 267B so that the pole end 268a thereof is opposed to the lower core layer 257 with a magnetic gap G therebetween in the ABS 251b, the base end 268b being provided to be magnetically connected to the lower core layer 257, as shown in FIGS. 16 and 17.
A protecting layer 269 made of alumina or the like is provided on the upper core layer 268.
In the inductive head h2, a recording current is supplied to the coil layer 266 to apply the recording current to the core layer from the coil layer 266. The inductive head h2 records magnetic signals on the magnetic recording medium such as a hard disk or the like by a leakage magnetic field from the magnetic gap G between the lower core layer 257 and the distal end of the upper core layer 268.
The magnetoresistive element layer 245 provided in the MR head h1 comprises a GMR (Giant Magnetoresistive) element exhibiting giant magnetoresistance. The GMR element has a multilayer structure formed by combining a plurality of materials. There are several types of structures creating giant magnetoresistance. Of these types, a type having a relatively simple structure and exhibiting a high rate of change in resistance with an external magnetic field is a spin valve system. The spin valve system includes a single spin valve system, and a dual spin valve system.
FIG. 18 is a sectional view showing the structure of a principal portion of an example of thin film magnetic heads comprising a conventional spin-valve thin film element, as viewed from the side opposite to a recording medium.
In FIG. 18, reference numeral MR1 denote s a spin-valve thin film element. The spin-valve thin film element MR1 is a top type single spin valve thin film element in which a free magnetic layer 125, a nonmagnetic conductive layer 124, a pinned magnetic layer 123, and an antiferromagnetic layer 122 are formed in turn from the lower gap layer 254 side.
In FIG. 18, reference numeral 121 denotes a base layer made of, for example, Ta (tantalum) or the like. The free magnetic layer 125 is formed on the base layer 121, and the nonmagnetic conductive layer 124 made of Cu or the like is formed on the free magnetic layer 125. The pinned magnetic layer 123 is formed on the nonmagnetic conductive layer 124, and the antiferromagnetic layer 122 is further formed on the pinned magnetic layer 123. A protecting layer 127 made of Ta or the like is formed on the antiferromagnetic layer 122 to form a lamination a10.
The pinned magnetic layer 123 is formed in contact with the antiferromagnetic layer 122 to cause an exchange coupling magnetic field (exchange anisotropic magnetic field) in the interface between the pinned magnetic layer 123 and the antiferromagnetic layer 122, thereby fixing magnetization of the pinned magnetic layer 123, for example, in the Y direction shown in the drawing.
In addition, hard bias layers 126 made of, for example, a Coxe2x80x94Pt (cobalt-platinum) alloy, i.e., permanent magnet films, are formed on both sides of the free magnetic layer 125. The hard bias layers 126 are formed for suppressing Barkhausen noise produced due to the formation of a plurality of magnetic domains in the free magnetic layer 125, and putting the free magnetic layer into a single magnetic domain state. For example, when the hard bias layers 126 are magnetized in the X1 direction shown in the drawing, magnetization of the free magnetic layer 125 is oriented in the X1 direction shown in the drawing by a leakage magnetic flux from the hard bias layers 126. This creates the relation that variable magnetization of the free magnetic layer 125 and fixed magnetization of the pinned magnetic layer 123 cross each other.
In FIG. 18, reference numeral 128 denotes a conductive layer made of Cr, Ta, Au, or the like.
In the spin-valve thin film element MR1, when the magnetization direction X1 of the free magnetic layer 125 is changed, electric resistance is changed with the angle with respect to the magnetization direction of the pinned magnetic layer 123 which is fixed in the Y direction, and a leakage magnetic field from the recording medium is detected by a change in voltage based on the change in the electric resistance value.
The central portion of the lamination a10 lies in a sensitive region which contributes to reproduction of a recording magnetic field from the magnetic recording medium, and which exhibits magnetoresistance, and defines the detection track width Tw.
FIG. 22 is a sectional view showing the structure of a principal portion of another example of thin film magnetic heads comprising another conventional spin valve thin film element, as viewed from the side opposite to a recording medium.
In FIG. 22, reference numeral MR2 denotes a spin-valve thin film element. The spin-valve thin film element MR2 is different from the spin-valve thin film element MR1 shown in FIG. 18 in that an antiferromagnetic layer 122, a pinned magnetic layer 153, a nonmagnetic conductive layer 124, and a free magnetic layer 165 are formed in turn from the lower gap layer 254 side, i.e., the spin-valve thin film element MR2 is a bottom type single spin valve thin film element.
In FIG. 22, reference numeral a11, denotes a lamination. The lamination all comprises the antiferromagnetic layer 122 formed on a base layer 121, the pinned magnetic layer 153 formed on the antiferromagnetic layer 122, the nonmagnetic conductive layer 124 formed on the pinned magnetic layer 153, the free magnetic layer 165 formed on the nonmagnetic conductive layer 124, and the protecting layer 127 formed on the free magnetic layer 165.
The pinned magnetic layer 153 of the spin-valve thin film element MR2 comprises a nonmagnetic intermediate layer 154, and first and second pinned magnetic layers 155 and 156 provided with the nonmagnetic intermediate layer 154 formed therebetween. The first pinned magnetic layer 155 is provided on the antiferromagnetic layer 122 side of the nonmagnetic intermediate layer 154; the second pinned magnetic layer 156 is provided on the nonmagnetic conductive layer 124 side of the nonmagnetic intermediate layer 154.
Each of the first and second pinned magnetic layers 155 and 156 comprises a NiFe alloy or the like. The nonmagnetic intermediate layer 154 comprises a nonmagnetic material such as Ru or the like.
The first and second pinned magnetic layers 155 and 156 preferably have different thicknesses. In FIG. 22, the thickness of the second pinned magnetic layer 156 is larger than the thickness of the first pinned magnetic layer 155.
An exchange coupling magnetic field (exchange anisotropic magnetic field) is produced in the interface between the first pinned magnetic layer 155 and the antiferromagnetic layer 122 to fix the magnetization direction of the first pinned magnetic layer 155 in the Y direction shown in the drawing due to the exchange coupling magnetic field with the antiferromagnetic layer 122. The second pinned magnetic layer 156 is antiferromagnetically coupled with the first pinned magnetic layer 155 to fix the magnetization direction in the direction opposite to the Y direction shown in the drawing.
The magnetization directions of the first and second pinned magnetic layer 155 and 156 are antiparallel to each other, and thus have the relation that the magnetic moments of the first and second pinned magnetic layers 155 and 156 are counteracted with each other. However, since the thickness of the second pinned magnetic layer 156 is larger than the thickness of the first pinned magnetic layer 155, spontaneous magnetization derived from the second pinned magnetic layer 156 is slightly left, bringing the pinned magnetic layer 153 into a ferrimagnetic state. Therefore, spontaneous magnetization is further amplified by the exchange coupling magnetic field with the antiferromagnetic layer 122 to fix the magnetization direction of the pinned magnetic layer 153 in the Y direction shown in the drawing.
The free magnetic layer 165 of the spin-valve thin film element MR2 comprises a ferromagnetic layer 166 made of a ferromagnetic material such as a NiFe alloy or the like, and a diffusion preventing layer 167 made of a ferromagnetic material such as Co or the like. The diffusion preventing layer 167 is provided on the nonmagnetic conductive layer 124 side. The magnetization of the free magnetic layer 165 is oriented in the X1 direction shown in the drawing by a leakage magnetic field from the hard bias layers 126.
In the spin-valve thin film element MR2, a sensing current is supplied to the free magnetic layer 165, the nonmagnetic conductive layer 124, and the pinned magnetic layer 153 from the conductive layers 128. A recording medium such as a hard disk or the like is moved in the Z direction shown in the drawing. When a magnetic field in the Y direction is applied due to a leakage magnetic field from the magnetic recording medium, magnetization of the free magnetic layer 165 is changed from the X1 direction to the Y direction to cause spin-dependent conduction electron scattering in the interface between the nonmagnetic conductive layer 124 and the free magnetic layer 165, and the interface between the nonmagnetic conductive layer 124 and the second pinned magnetic layer 156, thereby changing the electric resistance and thus detecting the leakage magnetic field from the recording medium.
The first and second pinned magnetic layers 155 and 156 are antiferromagnetically coupled with each other to have the relation that magnetic moments of the first and second pinned magnetic layers 155 and 156 are counteracted with each other. However, since the thickness of the second pinned magnetic layer 156 is larger than the thickness of the first pinned magnetic layer 155, spontaneous magnetization derived from the second pinned magnetic layer 156 is slightly left, bringing the pinned magnetic layer 153 into a ferrimagnetic state. Therefore, spontaneous magnetization is further amplified by the exchange coupling magnetic field with the antiferromagnetic layer 122 to fix the magnetization direction of the pinned magnetic layer 153 in the Y direction shown in the drawing, and improve the stability of the spin-valve thin film element MR2.
FIG. 23 is a sectional view showing the structure of a principal portion of a further example of thin film magnetic heads comprising another conventional spin valve thin film element, as viewed from the side opposite to a recording medium.
In FIG. 23, reference numeral MR3 denotes a spin-valve thin film element. The spin-valve thin film element MR3 is different from the spin-valve thin film element MR2 shown in FIG. 22 in the structure of a free magnetic layer and in that no backed layer is provided between the free magnetic layer and a protecting layer.
In FIG. 23, reference numeral a12 denotes a lamination. The lamination a12 comprises the antiferromagnetic layer 122 formed on a base layer 121, the pinned magnetic layer 153 formed on the antiferromagnetic layer 122, the nonmagnetic conductive layer 124 formed on the pinned magnetic layer 153, the free magnetic layer 175 formed on the nonmagnetic conductive layer 124, and the protecting layer 127 formed on the free magnetic layer 175.
The free magnetic layer 175 of the spin-valve thin film element MR3 comprises a nonmagnetic intermediate layer 176, and first and second free magnetic layers 177 and 178 provided with the nonmagnetic intermediate layer 176 formed therebetween.
The first free magnetic layer 177 is provided on the protecting layer 127 side of the nonmagnetic intermediate layer 176; the second free magnetic layer 178 is provided on the nonmagnetic conductive layer 124 side of the nonmagnetic intermediate layer 176. The second free magnetic layer 178 comprises a diffusion preventing layer 179 and a ferromagnetic layer 180.
The first free magnetic layer 177 comprises a ferromagnetic materials such as a NiFe alloy or the like, and the nonmagnetic intermediate layer 176 comprises a nonmagnetic material such as Ru or the like. Each of the diffusion preventing layer 179 and the ferromagnetic layer 180 comprises a ferromagnetic material. For example, the diffusion preventing layer 179 is made of a CoFe alloy, and the ferromagnetic layer 180 is made of a NiFe alloy.
The thickness of t2 the second free magnetic layer 178 is larger than the thickness t1 of the first free magnetic layer 177.
If saturation magnetizations of the first and second free magnetic layers 177 and 178 are M1 and M2, respectively, the magnetic thicknesses of the first and second free magnetic layers 177 and 178 are M1t1 and M2t2, respectively. Since the second free magnetic layer 178 comprises the diffusion preventing layer 179 and the ferromagnetic layer 180, the magnetic thickness M2t2 of the second free magnetic layer 178 is the sum of the magnetic thickness of the diffusion preventing layer 179, and the magnetic thickness of the ferromagnetic layer 180.
The free magnetic layer 175 is formed so that the magnetic thicknesses of the first and second free magnetic layers 177 and 178 have the relation M2t2 greater than M1t1. In addition, the first and second free magnetic layers 177 and 178 can be coupled antiferromagnetically with each other. Namely, when magnetization of the first free magnetic layer 177 is oriented in the X1 direction shown in the drawing by the hard bias layers 126, magnetization of the second free magnetic layer 178 is oriented in the direction opposite to the X1 direction shown in the drawing.
Furthermore, the magnetic thicknesses of the first and second free magnetic layers 177 and 178 have the relation M2t2 greater than M1t1, magnetization of the second free magnetic layer 178 remains, and thus magnetization of the whole free magnetic layer 175 is oriented in the X1 direction. In this case, the effective thickness of the free magnetic layer 175 is represented by (M2t2xe2x88x92M1t1).
In this way, the first and second free magnetic layer 177 and 178 are coupled with each other ferromagnetically so that the magnetization directions are antiparallel to each other, and the magnetic thicknesses thereof have the relation M2t2 greater than M1t1, thereby causing an artificial ferrimagnetic state. Therefore, there is the relation that the magnetization directions of the free magnetic layer 175 and the pinned magnetic layer 153 cross each other.
In the spin-valve thin film element MR3, when the magnetization direction X1 of the free magnetic layer 175 is changed by a leakage magnetic field from a recording medium such as a hard disk or the like, the electric resistance is changed based on the relation to magnetization of the pinned magnetic layer 153 which is fixed in the Y direction shown in the drawing, thereby detecting the leakage magnetic field from the recording medium by a change in voltage based on the change in the electric resistance value.
Furthermore, the free magnetic layer 175 comprises the first and second free magnetic layers 177 and 178 which are coupled with each other antiferromagnetically, and thus the magnetization direction of the whole free magnetic layer 175 is changed by a small external magnetic field, increasing the sensitivity of the spin-valve thin film element.
In the spin-valve thin film element MR1 shown in FIG. 18, the hard bias layers 126 are formed in contact with the sides of the lamination a10. The portions of the hard bias layers 126 which are respectively joined to the upper portions of the sides of the lamination a10 have a sectional shape in which the thickness gradually decreases in the direction to the upper edges of the sides. The tips 126a of the hard bias layers 26 which are respectively joined to the upper edges of the sides of the lamination a10 have a pointed sectional shape.
Therefore, a leakage magnetic flux from the hard bias layers 126 joined to the upper edges of the sides of the lamination a10 is absorbed by the upper shielding layer 257 provided above the spin-valve thin film element MR1 from the tips 126a to form a flow of the magnetic flux as shown by an arrow C in FIG. 18, thereby causing the problem of decreasing the effective magnetic field applied to the free magnetic layer 125. It is thus difficult to sufficiently control the magnetic domain of the free magnetic layer 125, causing the problem of low stability.
In addition, magnetizations at the tips 126a of the hard bias layers 126 near the upper edge of the sides of the lamination a10 are respectively oriented in the directions shown by arrows A and D in FIG. 18. This causes a magnetic field (arrow B) which leaks from the tips 126a and is absorbed by the.bottoms of the tips 126a, and a magnetic flux (arrow E) which leaks from the bottoms and is absorbed by the tips 126a. These magnetic fields apply a magnetic field to both ends of the free magnetic layer 125 in the direction opposite to the desired direction of a magnetic field to be applied to the free magnetic layer 125, thereby causing the problems of adversely affecting control of the magnetic domain of the free magnetic layer 125 and deteriorating stability.
Also, in the spin-valve thin film element MR2 shown in FIG. 22, like in the spin valve thin film element MR1, magnetizations at the tips 126a of the hard bias layers 126 near the upper edges of the sides of the lamination all are respectively oriented in the directions shown by arrows A and D. This causes a dipole magnetic field (external antimagnetic field), i.e., a magnetic field (arrow B) which leaks from the tips 126a and is absorbed by the bottoms of the tips 126a, and a magnetic flux (arrow E) which leaks from the bottoms and is absorbed by the tips 126a. These magnetic fields apply a magnetic field to both ends of the free magnetic layer 165 in the direction opposite to the desired direction of a magnetic field to be applied to the free magnetic layer 165, thereby causing the problems of adversely affecting control of the magnetic domain of the free magnetic layer 165 and making abnormal the reproduced waveform at both ends of the track width Tw.
In the spin-valve thin film element MR3 shown in FIG. 23, a strong magnetic field is applied to the first free magnetic layer 177 from the tips 126a of the hard bias layers 126 near the upper edges of the sides of the lamination a12, to apply, to the first free magnetic layer 177, magnetization in the direction opposite to the desired direction of a magnetic field to be applied to the first free magnetic layer 177. If the magnetic field of the hard bias layers 126 is higher than a spin flop magnetic field (HSt), therefore, a magnetic field is applied to both ends (the portions near the hard bias layers 126) of the first free magnetic layer 177 in the direction opposite to the desired direction of the magnetization applied to the first free magnetic layer 177. As a result, the magnetization direction in the central portion of the first free magnetic layer 177 is arranged in the direction opposite to the magnetization direction of the second free magnetic layer 178, while the magnetization directions at both ends are disturbed. When the magnetization directions at both ends of the first free magnetic layer 177 are disturbed, the magnetization direction in the central portion of the second free magnetic layer 178, in which the magnetization direction is antiparallel (X1 direction) to the magnetization direction of the first free magnetic layer 177, is arranged in the direction (X1 direction) opposite to the magnetization direction of the first free magnetic layer, while the magnetization directions at both ends are disturbed. Thus, the magnetization directions at both ends of the first and second free magnetic layers 177 and 178 are not brought into the antiparallel state, thereby causing the problems of unstable reproduced waveforms at both ends of the track width Tw, servo error, etc.
The spin flop magnetic field will be described below with reference to FIG. 24. FIG. 24 is a diagram showing a M-H curve of a free magnetic layer. The M-H curve indicates changes in magnetization M of the free magnetic layer 175 when an external magnetic field H was applied to the free magnetic layer 175 of the spin-valve thin film element MR3 shown in FIG. 23 in the direction of the track width Tw. The external magnetic field H corresponds to a bias magnetic field form the hard bias layers 126.
In FIG. 24, an arrow F1 shows the magnetization direction of the first free magnetic layer 177, and arrow F2 shows the magnetization direction of the second free magnetic layer 178.
FIG. 24 reveals that with a low external magnetic field H, the first and second free magnetic layers 177 and 178 are brought into the antiferromagnetic coupling state, i.e., in the state wherein the directions of the arrows F1 and F2 are antiparallel to each other. However, with the value of an external magnetic field H over a predetermined value, the directions of the arrows F1 and F2 are not brought into the antiparallel state, thereby breaking the antiferromagnetic coupling state of the first and second free magnetic layers 177 and 178, failing to maintain the ferrimagnetic state. This is referred to as xe2x80x9cspin flop transitionxe2x80x9d. The external magnetic field with which the spin flow transition occurs is the spin flop magnetic field denoted by Hsf in FIG. 24. With the external magnetic filed H higher than the spin flop magnetic field, the F1 direction is further rotated to the direction parallel to the F2 direction, i.e., the direction 180 different from the initial F1 direction, thereby completely breaking the ferrimagnetic state. This is referred to as the xe2x80x9csaturation magnetic fieldxe2x80x9d, which is denoted by Hs in FIG. 24. Therefore, the magnetization directions at both ends of the first and second free magnetic layers 177 and 178 shown in FIG. 23 have, for example, the relation between Hsf and Hs shown in FIG. 24.
The present invention has been achieved for solving the above problems in consideration of the above-described situation, and an object of the present invention is to provide a spin-valve thin film element with excellent stability which causes little decrease in an effective magnetic field applied to a free magnetic layer, and little magnetic field exerting a magnetic field in the direction opposite to the magnetization direction of the free magnetic layer near the upper edges of the sides of a lamination, and which permits sufficient control of the magnetic domain of the free magnetic layer. Another object of the present invention is to provide a method of manufacturing the spin-valve thin film element.
A further object of the present invention is to provide a thin film magnetic head comprising the spin-valve thin film element.
In order to achieve the objects, a spin-valve thin film element of the present invention comprises an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer so that the magnetization direction is fixed by an exchange coupling magnetic field with the antiferromagnetic layer, and a nonmagnetic conductive layer formed on the pinned magnetic layer and a free magnetic layer provided therebetween, which are laminated in turn on a substrate to form a lamination comprising at least the antiferromagnetic layer, the pinned magnetic layer, the nonmagnetic conductive layer, and the free magnetic layer; hard bias layers formed on both sides of the lamination, for arranging the magnetization direction of the free magnetic layer in the direction crossing the magnetization direction of the pinned magnetic layer; and conductive layers respectively formed on the hard bias layers, for supplying a sensing current to the lamination; wherein the hard bias layers are arranged at the same level as the free magnetic layer, and the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions lower than the upper edges of the sides of the lamination.
The sentence xe2x80x9cthe hard bias layers are formed at the same level as the free magnetic layerxe2x80x9d means the state in which at least the hard bias layers are joined to the free magnetic layer, the state including a state in which the thickness of the junctions between the hard bias layers and the free magnetic layer is smaller than the thickness of the free magnetic layer.
The terms xe2x80x9cthe upper surfaces of the hard bias layersxe2x80x9d means the surfaces opposite to the substrate side.
The terms xe2x80x9cjunctionxe2x80x9d means not only connection in direct contact the lamination but also connection therewith through, for example, a base layer, an intermediate layer, or the like.
In the spin-valve thin film element, the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions lower than the upper edges of the sides of the lamination. Therefore, a leakage magnetic flux from the hard bias layers is little absorbed by an upper shielding layer, thereby preventing a decrease in the effective magnetic field applied to the free magnetic layer, and easily putting the free magnetic layer into a single magnetic domain state. The spin-valve thin film element permits sufficient control of the magnetic domain of the free magnetic layer, and exhibits excellent stability.
Also, in the spin-valve thin film element, the hard bias layers are arranged at the same level as the free magnetic layer to readily apply a strong bias magnetic field to the free magnetic layer, thereby easily putting the free magnetic layer into a single magnetic domain state, and decreasing the occurrence of Barkhausen noise.
Furthermore, in the spin-valve thin film element, the upper surfaces of the hard bias layers are preferably joined to the sides of the lamination at the same positions as or positions lower than the uppermost position of the hard bias layers.
In the spin-valve thin film element, therefore, a magnetic field exerting a magnetic field in the direction opposite to the magnetization direction of the free magnetic layer near the upper edges of the sides of the lamination is less produced, thereby easily putting the free magnetic layer into a single magnetic domain state. The spin-valve thin film element thus has the excellent property that the magnetic domain of the free magnetic layer can be more sufficiently controlled.
In the spin-valve thin film element, preferably, the thickness of the hard bias layers is larger than the thickness of the free magnetic layer in the thickness direction thereof, and the upper surfaces of the hard bias layers are arranged at a larger distance from the substrate than the upper side of the free magnetic layer.
In the spin-valve thin film element, therefore, a stronger bias magnetic field can be easily applied to the free magnetic layer, thereby easily putting the free magnetic layer into the single magnetic domain state and decreasing the occurrence of Barkhausen noise.
In the spin-valve thin film element, the lower sides of the hard bias layers are preferably arranged at positions lower than the lower side of the free magnetic layer.
In the spin-valve thin film element, therefore, a strong bias magnetic field can be easily applied to the free magnetic layer, thereby easily putting the free magnetic layer into the single magnetic domain state and further decreasing the occurrence of Barkhausen noise.
In the spin-valve thin film element, the antiferromagnetic layer comprises an alloy represented by the formula Xxe2x80x94Mn (wherein X represents one element selected from Pt, Pd, Ru, Ir, Rh, and Os), wherein X is preferably in the range of 37 to 63 atomic %.
Furthermore, in the spin-valve thin film element, the antiferromagnetic layer comprises an alloy represented by the formula Xxe2x80x2xe2x80x94Ptxe2x80x94Mn (wherein Xxe2x80x2 represents at least one element selected from Pd, Cr, Ru, Ni, Ir, Rh, Os, Au, Ag, Ne, Ar, Xe, and Kr), wherein the total of Xxe2x80x2 and Pt is preferably in the range of 37 to 63 atomic %.
The spin-valve thin film element comprising the antiferromagnetic layer made of an alloy represented by the formula Xxe2x80x94Mn or Xxe2x80x2xe2x80x94Ptxe2x80x94Mn has excellent properties such as a high exchange coupling field, a high blocking temperature, and excellent corrosion resistance, as compared with use of a NiO alloy, a FeMn alloy, a NiMn alloy, or the like, which is conventionally used for the antiferromagnetic layer.
In the spin-valve thin film element, an intermediate layers of Ta or Cr may be respectively provided between the hard bias layers and the conductive layers.
In use of Cr for the conductive layers, the intermediate layer of Ta functions as a diffusion barrier in a thermal process such as resist curing in the subsequent step to prevent deterioration in magnetic properties of the hard bias layers. In use of Ta for the conductive layers, the intermediate layer of Cr has the effect of readily depositing Ta crystals having a low-resistance body centered cubic structure.
In addition, in the spin-valve thin film element, bias base layers made of Cr may be provided between the hard bias layers and the lamination, and between the hard bias layers and the substrate.
The bias base layers of Cr having a body centered cubic crystal structure (bcc structure) increase the coercive force and remanence ratio of the hard bias layers, and thus increase a bias magnetic field necessary for putting the free magnetic layer into a single magnetic domain state.
The spin-valve thin film element may have a dual structure in which a nonmagnetic conductive layer, a pinned magnetic layer and an antiferromagnetic layer are formed on either side of the free magnetic layer in the thickness direction.
This spin-valve thin film element comprises two combinations of the three layers including the free magnetic layer, the nonmagnetic conductive layer and the pinned magnetic layer, and thus exhibits higher xcex94MR (rate of change in resistance) and is capable of comply with high-density recording.
In the spin-valve thin film element, at least one of the pinned magnetic layer and the free magnetic layer may be divided into two layers with a nonmagnetic intermediate layer therebetween so that the two divided layers are brought into an artificial ferrimagnetic state in which the magnetization directions are 180xc2x0 different from each other.
In the spin-valve thin film element in which at least the pinned magnetic layer is divided into two layers with a nonmagnetic intermediate layer provided therebetween, one of the two divided pinned magnetic layers has the function to fix the other pinned magnetic layer in a proper direction to maintain the pinned magnetic layers in a stable state.
On the other hand, in the spin-valve thin film element in which at least the free magnetic layer is divided into two layers with a nonmagnetic intermediate layer provided therebetween, an exchange coupling magnetic field occurs between the two divided free magnetic layers to create a ferrimagnetic state, thereby decreasing the magnetic thickness to achieve reversal with high sensitivity to an external magnetic field.
In the spin-valve thin film element, the lamination preferably comprises a backed layer comprising a nonmagnetic conductive material in contact with the side of the free magnetic layer opposite to the nonmagnetic conductive layer side.
In this spin-valve thin film element, therefore, in the lamination, the center height of a flow of a sensing current from the conductive layers can be changed to the backed layer side from a position on the pinned magnetic layer side in the case of no backed layer provided. It is thus possible to decrease the intensity of a sensing current magnetic field at the position of the free magnetic layer, and decrease the contribution of the sensing current magnetic field to variable magnetization of the free magnetic layer. Therefore, the spin-valve thin film element has the excellent property that the direction of variable magnetization of the free magnetic layer can easily be corrected to any desired direction with low asymmetry, thereby facilitating control of the direction of variable magnetization of the free magnetic layer.
Furthermore, in the single spin-valve thin film element, the conductive layers are preferably coated to extend toward the central portion of the surface of the lamination from both sides thereof.
In this spin-valve thin film element, a sensing current from the conductive layers little flows to the joints between the hard bias layers and the lamination, thereby increasing the ratio of the sensing current flowing directly to the lamination. In this case, joint resistance which does not contribute to magnetoresistance can be decreased by increasing the joint area between the lamination and the conductive layers, improving reproduction characteristics.
In the single spin-valve thin film element or the bottom type single spin valve thin film element in which the antiferromagnetic layer is formed on the substrate side, the upper surfaces of the hard bias layers are jointed to the sides of the lamination at positions between the upper and lower surfaces of the free magnetic layer.
In this spin-valve thin film element, a dipole magnetic field (external demagnetizing field) exerting a magnetic field in the direction opposite to the desired direction of magnetization imparted to the free magnetic layer is less produced near the upper edges of the sides of the lamination. It is thus possible to improve disturbance in the magnetization directions at both ends of the free magnetic layer, which is due to the dipole magnetic field, and orient magnetization of the free magnetic layer in one direction by a leakage magnetic field from the hard bias layers. Therefore, the free magnetic layer can easily be put into a single magnetic domain state, and the magnetic domain of the free magnetic layer can be more sufficiently controlled. It is also possible to prevent the occurrence of abnormality in the produced waveforms at both ends of the track width, and improve stability of the reproduced waveforms.
In the single spin-valve thin film element or the bottom type single spin valve thin film element in which the antiferromagnetic layer is formed on the substrate side, the upper surfaces of the hard bias layers are preferably joined to the sides of the lamination at positions between the upper surface of the free magnetic layer and the center of the free magnetic layer in the thickness direction thereof.
In this spin-valve thin film element, it is thus possible to improve disturbance in the magnetization directions at both ends of the free magnetic layer, which is due to the dipole magnetic field, and readily apply a strong bias magnetic field to the free magnetic layer. Therefore, the free magnetic layer can easily be put into a single magnetic domain state, and stability of reproduced waveforms can be further improved.
In the single spin-valve thin film element or the bottom type single spin valve thin film element in which the antiferromagnetic layer is formed on the substrate side, preferably, the two divided free magnetic layers with the nonmagnetic intermediate layer provided therebetween are brought into the ferrimagnetic state in which the magnetization directions are 180xc2x0 different. Where the free magnetic layer of the two free magnetic layers divided by the nonmagnetic intermediate layer, which contacts the nonmagnetic conductive layer, is referred to as a xe2x80x9csecond free magnetic layerxe2x80x9d, and the other is referred to as a xe2x80x9cfirst free magnetic layerxe2x80x9d, the upper surfaces of the hard bias layers are preferably joined to the sides of the lamination at positions between the upper and lower surfaces of the second free magnetic layer.
In this spin-valve thin film element, it is thus possible to avoid a strong magnetic field in the direction opposite to the desired direction of magnetization imparted to the first free magnetic layer from being applied to the ends of the hard bias layers near the upper edges of the sides of the lamination, and improve disturbance in the magnetization directions at both ends of the first free magnetic layer. It is also possible to prevent the magnetization directions at both ends of the second free magnetic layer, which are opposite to the magnetization direction of the first free magnetic layer, from being disturbed due to disturbance in the magnetization directions at both ends of the first free magnetic layer. Furthermore, the antiferromagnetic coupling between the first and second free magnetic layers can stably be maintained to maintain the free magnetic layers in the ferrimagnetic state. It is thus possible to prevent the occurrence of abnormality in reproduced waveforms at both ends of the track width without deteriorating the sensitivity of the spin-valve thin film element, and improve stability of the reproduced waveforms.
In the single spin-valve thin film element or the bottom type single spin valve thin film element in which the antiferromagnetic layer is formed on the substrate side, the upper surfaces of the hard bias layers are preferably joined to the sides of the lamination at positions between the upper surface of the second free magnetic layer and the center thereof in the thickness direction.
In this spin-valve thin film element, it is thus possible to improve disturbance in the magnetization directions at both ends of the first free magnetic layer, and prevent the magnetization directions at both ends of the second free magnetic layer, which are opposite to the magnetization direction of the first free magnetic layer, from being disturbed due to disturbance in the magnetization directions at both ends of the first free magnetic layer. Furthermore, a strong bias magnetic field can be applied to the second free magnetic layer to impart a magnetic field in the same direction as the desired direction of magnetization imparted thereto, thereby improving the sensitivity of the spin-valve thin film element. It is also possible to prevent the occurrence of abnormality in reproduced waveforms at both ends of the track width, and improve stability of the reproduced waveforms.
Furthermore, in the single spin-valve thin film element or the bottom type single spin valve thin film element in which the antiferromagnetic layer is formed on the substrate side, where saturation magnetization and thickness of the second free magnetic layer are M2 and t2, respectively, and saturation magnetization and thickness of the first free magnetic layer are M1 and t1, respectively, the relation M2xc2x7t2 greater than M1xc2x7t1 is preferably satisfied.
In this spin-valve thin film element, the magnetic thickness of the second free magnetic layer is larger than that of the first free magnetic layer, and a difference between the magnetic thicknesses of the first and second free magnetic layers becomes the effective magnetic thickness of the free magnetic layer. Therefore, the thicknesses of the first and second free magnetic layers can be appropriately controlled to decrease the effective thickness of the free magnetic layer, thereby permitting a change in the magnetization direction of the free magnetic layer with a small external magnetic field. It is thus possible to improve the sensitivity of the spin-valve thin film element.
In addition, since the thickness of the whole free magnetic layer can be increased to some extent, the rate of change in resistance is not significantly decreased, and the upper surfaces of the hard bias layers, which can improve the sensitivity of the spin-valve thin film element, are preferably joined to the sides of the lamination at positions between the upper and lower surfaces of the second free magnetic layer.
The single spin-valve thin film element may be a bottom type in which the antiferromagneic layer, the pinned magnetic layer, and the nonmagnetic conductive layer, and the free magnetic layer are laminated in this order from the substrate side.
In this spin-valve thin film element, it is possible to increase the ratio of the sensing current supplied to the lamination without through the antiferromagnetic layer having high resistivity, and decrease the shunt components of the sensing current which flow directly into portions near the pinned magnetic layer, the nonmagnetic conductive layer and the free magnetic layer, which are formed below the antiferromagnetic layer, through the hard bias layers, as compared with a top type in which the free magnetic layer, the nonmagnetic conductive layer, the pinned magnetic layer, and the antiferromagnetic layer are laminated in this order from the substrate side. It is thus possible to prevent side reading, and further comply with high-density magnetic recording.
In order to achieve the objects, the present invention provides a method of manufacturing a spin-valve thin film element comprising the steps of forming, on a substrate, layered films comprising at least an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer so that the magnetization direction is fixed by an exchange coupling magnetic field with the antiferromagnetic layer, and a free magnetic layer formed on the pinned magnetic layer with a nonmagnetic conductive layer provided therebetween; forming lift off resist on the layered films; removing portions not covered with the lift off resist by ion milling to form a trapezoidal lamination; forming hard bias layers on both sides of the lamination by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof so that they are arranged in the same layer level as the free magnetic layer, and the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions lower than the upper edges of the sides of the lamination; and forming conductive layers on the hard bias layers with a target inclined at an angle with the substrate by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof.
The method of manufacturing a spin-valve thin film element can easily obtain the above-described spin-valve thin film element.
In order to achieve the objects, the present invention also provides a method of manufacturing a spin-valve thin film element comprising the steps of forming layered films comprising at least an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer so that the magnetization direction is fixed by an exchange coupling magnetic field with the antiferromagnetic layer, and a free magnetic layer formed on the pinned magnetic layer with a nonmagnetic conductive layer provided therebetween; forming, on the layered films, lift off resist in which notch portions are formed in the lower surface; removing portions not covered with the lift off resist by ion milling to form a trapezoidal lamination; forming hard bias layers on both sides of the lamination by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof so that they are arranged in the same layer level as the free magnetic layer, and the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions lower than the upper edges of the sides of the lamination; and forming conductive layers on the hard bias layers and the portions of the lamination corresponding to the notch portions of the lift off resist with a target inclined at an angle with the substrate by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof.
In the method of manufacturing a spin-valve thin film element, the resist step of forming once the lift off resist having the cur portion formed therein on the layered films permits the formation of a resist pattern, etching of the lamination by ion milling, and the formation of the hard bias layers and the conductive layers in desired shapes by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof, in which the target is selectively opposed to the substrate in either of a noninclined or inclined state with the set inclination angle, to obtain the above-described spin-valve thin film element.
In this method, the width dimension of each of the notch portions, i.e., the width dimension of each of the notch portions which do not contact the lamination, in the sideward direction of the lamination, i.e., the dimension in the track width direction, can be set relative to the width dimension of the lift off photoresist in the sideward direction of the lamination to set the length dimension of each of the overlay portions of the conductive layers which are formed in the notch portions to extent toward the center of the surface of the lamination from the both sides thereof.
Therefore, one formation of the photoresist (lift off photoresist) enables the formation of the lamination, the hard bias layers, and the conductive layers in desired shapes, and the hard bias layers and the conductive layers can be formed in desired shapes by the sputtering in which the target is selectively opposed to the substrate in either of the noninclined or inclined state. Thus the spin-valve thin film element can easily be obtained by a small number of steps.
In order to achieve the objects, the present invention also provides a method of manufacturing a spin-valve thin film element comprising the steps of forming, on a substrate, layered films comprising at least an antiferromagnetic layer, a pinned magnetic layer formed in contact with the antiferromagnetic layer so that the magnetization direction is fixed by an exchange coupling magnetic field with the antiferromagnetic layer, and a free magnetic layer formed on the pinned magnetic layer with a nonmagnetic conductive layer provided therebetween; forming, on the layered films, first lift off resist in which notch portions are formed in the lower surface opposing the layered films; removing portions not covered with the first lift off resist by ion milling to form a trapezoidal lamination; forming hard bias layers on both sides of the lamination by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof so that they are arranged in the same layer level as the free magnetic layer, and the upper surfaces of the hard bias layers are joined to the sides of the lamination at positions lower than the upper edges of the sides of the lamination; separating the first lift off resist; forming second lift off resist in which the sideward dimension of a portion in contact with the layered films is smaller than that of the first lift off resist, and notch portions are formed in the lower surface opposing the layered films; and forming conductive layers the portions not covered with the second lift off resist by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof.
In the method of manufacturing a spin-valve thin film element, the two resist steps of respectively forming the two types of lift off resist having the cur portions formed therein and having different width dimensions on the layered films permit the formation of the lamination and the hard bias layers, and the formation of the conductive layers in. desired shapes by any one sputtering method of an ion beam sputtering method, a long throw sputtering method, and a collimation sputtering method, or a combination thereof, in which the target is selectively opposed to the substrate in either of a noninclined or inclined state, to obtain the above-described spin-valve thin film element.
In this method, the dimension of each of the notch portions of the first lift off resist in the track width direction, i.e., the width dimension of each of the notch potions which do not contact the lamination, in the sideward direction of the lamination can be set relative to the width dimension of the lift off photoresist in the sideward direction of the lamination, i.e., the dimension in the track width, and the incidence angle of an ion beam for ion milling can be set to set the dimension of the lamination in the direction of the track width, and the shape of the hard bias layers. Similarly, the dimension of the second lift off resist in the direction of the track width can be set to set the length dimension of the overlay portions of the conductive layers which are formed to extent toward the center of the surface of the lamination from the both sides thereof.
The manufacturing method may further comprise the steps of removing portions of the surface of the lamination corresponding to the notch portions of the first lift off resist or the second lift off resist by ion milling or reverse sputtering after the step of forming the hard bias layers. This permits cleaning of the protecting layer as the uppermost layer and the backed layer by ion milling or reverse sputtering to achieve sufficient connection between electrode layers and the backed layer, thereby decreasing contact resistance.
In the method of manufacturing a spin-valve thin film element, the step of forming the lamination preferably comprises forming the backed layer made of a nonmagnetic conductive material on the side of the free magnetic layer opposite to the nonmagnetic conductive layer side.
In order to achieve the objects, the present invention further provides a thin film magnetic head comprising the above-described spin-valve thin film element.
This thin film magnetic head enables sufficient control of the magnetic domain of the free magnetic layer, and exhibits excellent stability.